Charles Frédéric Gerhardt

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Portrait of Charles Frédéric Gerhardt
The grave of Charles Gerhardt on the Cimetière Sainte-Hélène de Strasbourg

Charles Frédéric Gerhardt (born August 21, 1816 in Strasbourg ; † August 19, 1856 there ) was an Alsatian chemist . Gerhardt, an organic chemist , realized that some of the molecular formulas previously used in organic chemistry were wrong. He improved the type theory (see below ) and realized that the boiling and melting points of organic compounds change evenly with each additional methylene group .

Life

His father was Samuel Gerhardt (1780–1847), initially a bank clerk in Strasbourg, then since 1825 a manufacturer in Hangenbieten . His mother was the widowed Charlotte Henriette Gerhardt (1785–1846), née Weber and previously married to Philipp Jacques Lobstein.

Gerhardt studied from 1831 at the polytechnic school in Karlsruhe , 1833 in Leipzig with Erdmann , in Giessen with Justus von Liebig and in Dresden .

From 1834 he worked in his father's white lead factory . He joined the military after an argument with his father. With money from German friends (probably also from Liebig) he was able to buy his way out of military service, transfer money to his father and do research with Liebig in Gießen (1836–1837). The complicated relationship with his father led to renewed disagreements, so that Gerhardt went to Paris in 1838 with a reference from Justus von Liebig. There he heard chemistry and physics lectures from Jean-Baptiste Dumas and César-Mansuète Despretz . In 1838 he became an assistant at Dumas at the Sorbonne . Through the mediation of his friend Auguste André Thomas Cahours , he was then accepted as an assistant in the laboratory of Eugène Chevreul in the Parisian botanical garden Jardin des Plantes . Due to the now improving possibilities for independent experimental work on the camphor-like substance Hellenin, from the root of the Inula hellenium and on succinic acid (succinylic acid). With his college friend he also did research on essential oils . In 1841 he received his doctorate, passed the licentiate examination and in 1844 became titular professor of chemistry in Montpellier . In 1844 he also met Auguste Laurent , with whom he remained friends until his death in 1853. For lack of money, the marriage with a woman from Montpellier did not materialize. Gerhardt finally married Jane Sander, the daughter of a Scotsman, in 1844.

In 1848 he left Montpellier and founded his school for practical chemistry, École de chimie pratique , in Paris . In 1855 he became professor of chemistry at the École Polytechnique in Strasbourg. On April 21, 1856 he became a corresponding member of the Académie des sciences .

Scientific achievements

Gerhardt had already examined rock samples for silicate at the age of eighteen.

Atomic mass, equivalents

In 1842 he published a treatise on chemical equivalents that was contrary to the doctrinal opinion. At that time the equivalent weights for the atoms were C = 6, O = 8, S = 16, Ca = 20. Since hydrogen was still considered a monatomic gas, Gerhardt found deviations in Avogadro's law for organic molecules in the gas phase. He assumed that organic molecules in the gas would need two parts by volume. Gerhardt also wrote that the majority of all older formulas for organic molecules were wrong, the formulas had to be halved. Before 1845 Leopold Gmelin used the empirical formulas C 2 O 4 ( carbon dioxide ), S 2 O 4 ( sulfur dioxide ), for aniline hydrochloride August Wilhelm von Hofmann (1842) gave the formula C 12 H 14 N 2 + H 2 Cl 2 .

Gerhardt demanded C = 12, O = 16, S = 32 for the atomic masses. Since Gerhardt misused the concept of the equivalent and also applied the wrong atomic masses for metal oxides, his ideas were rejected by other chemists.

Through an elaboration by Auguste Laurent , who regarded hydrogen , oxygen , chlorine , and nitrogen as diatomic gases and called these diatomic gases as molecules, the densities, molecular masses and molecular formulas of organic molecules could be correctly determined.

The correct spelling for empirical formulas only became established in magazines and books from 1850 onwards.

Residual theory, basicity law, type theory

In the scientific debate on the theory of reactions of organic substances, Gerhardt supported Laurent's core theory . He added the core theory to the remainder theory . When organic molecules are split off, which remain constant in the carbon core, stable inorganic compounds such as water, ammonia , hydrogen chloride and carbon dioxide emerge. The atomic complexes of the carbon (the residues) remain intact. Since exact structural formulas for organic molecules were not yet known, Gerhardt assumed that the split-off residues are closely related in the molecule. So he took several formulas for one molecule.

Gerhardt also recognized that the emerging element in a chemical reaction must correspond to the entering element in a stoichiometric amount (e.g. conversion of ethanol to ethyl bromide , residual group: water, entry group: bromide). In addition to the substitution, he also recognized regular relationships in addition. When sulfuric acid or nitric acid acted on organic compounds (e.g. alcohols, hydrocarbons), he was able to demonstrate changes in the properties of these substances. These findings led to the so-called basicity law . The basicity of paired connections is equal to the sum of the basicities of paired bodies, less one. At that time, the basicity was identical to the number of hydrogen atoms that could be split off from an acid. Sulfuric acid had the basicity of two. When combined with an organic sulfonic acid , the basicity of the sulfonic acid was only one.

In his type theory (chemistry) , which was a supplement to the ideas of Jean Baptiste Dumas , Gerhardt took the view that there should be four types of compounds: hydrogen (HH), hydrogen halide (H-Cl), water (HOH), ammonia (NH 3 ). By replacing a hydrogen atom, four types of compounds can be derived. Mixed types can also be created by doubling individual types.

Together with Laurent, Gerhardt took the view that atoms also have different valences in organic molecules and that the conversion of substances can be expressed in chemical equations.

Gerhardt introduced the term homologue series in 1843 . Gerhardt has also written a textbook on organic chemistry.

Analyzes and syntheses

With Cahours, Gerhardt discovered the secondary component p -cyymol in caraway oil in 1841 , which Dumas had already synthesized from camphor in 1832 .

  • In 1842 Gerhardt discovered the quinoline in quinine .
  • In the same year Gerhardt coined the term acetyl when he made the acetyl chloride from potassium acetate and phosphorus trichloride .
  • In 1843, Gerhardt produced the acetanilide from acetyl chloride and aniline. He now synthesized many more anilides, i. H. Amides which contain aniline as an amino group. With the acetyl chloride many amides and diamides could now be produced in organic chemistry.

He made his first attempt to produce the mixed acetylsalicylic anhydride from acetyl chloride and sodium salicylate in 1853. The intention for this was the linking method discovered by AW Williamson in 1850 . The main product he received was a solidifying, water-miscible oil that spontaneously disintegrated again into salicylic and acetic acid in bicarbonate solution.

Works (selection)

literature

  • Max Bloch: Gerhardt and Laurent. In: Günther Bugge (ed.): The book of great chemists. Volume 2: From Liebig to Arrhenius. Verlag Chemie, Weinheim et al. 1930, pp. 92 ff. (Reprint. Ibid 1974, ISBN 3-527-25021-2 ).
  • Édouard Grimaux : Charles Gerhardt, sa vie, son oeuvre, sa correspondance, 1816-1856 , 1900

Web links

Individual evidence

  1. ^ Günther Kerstein :  Gerhardt, Carl (Charles) Friedrich. In: New German Biography (NDB). Volume 6, Duncker & Humblot, Berlin 1964, ISBN 3-428-00187-7 , p. 282 f. ( Digitized version ).
  2. ↑ About the Hellenin. In Pharmaceutical Centralblatt 11 , 309-312 (1840)
  3. ^ List of members since 1666: Letter G. Académie des sciences, accessed on November 18, 2019 (French).
  4. ↑ Studies on the chemical classification of organic substances. Theoretical part. in Journal für Praktische Chemie 27 , 439-464 (1842)
  5. ↑ On the chemical classification of organic substances. in: Journal für Praktische Chemie 30 , 1-10 (1843)
  6. ↑ August Kekulé : Textbook of organic chemistry or the chemistry of carbon compounds. Volume 1. Enke, Erlangen 1861, p. 66 ff.
  7. ↑ by Gebhardt referred to as "anhydrous salicylic acid-acetic acid"
  8. ↑ Conversion of acetyl chloride (electrophile) with sodium acetate (nucleophile) results in the anhydride of acetic acid. The mixed anhydride is to be expected from acetyl chloride and sodium salicylate.
  9. ↑ Ch. Gerhardt, Investigations on the anhydrous organic acids, Annalen der Chemie und Pharmacie 87 , 149-179 (1853) on p. 162.
personal data
SURNAME Gerhardt, Charles Frédéric
BRIEF DESCRIPTION French chemist
DATE OF BIRTH August 21, 1816
PLACE OF BIRTH Strasbourg
DATE OF DEATH August 19, 1856
Place of death Strasbourg